A number of medications comprise two ingredients which are not mixed together until shortly prior to administration. In many instances, one of the two ingredients comprises a solid, usually a powder, whereas the other ingredient constitutes a liquid in which the solid ingredient is dissolved. Less frequently, the medication may comprise two liquids to be mixed together.
Administration of a dual-ingredient medication of this kind can be accomplished with a conventional syringe by first loading one ingredient into the syringe, then adding the second ingredient, shaking the syringe or otherwise agitating the contents to achieve effective mixing, and subsequently dispensing the complete dual-ingredient medication mixture in the usual manner. This procedure, however, presents substantial difficulties, including possible contamination and loss of sterilization. For example, using a conventional syringe of the kind that is filled through a fill needle connected to the outlet orifice of the syringe, it is necessary to replace the needle after the first ingredient has been drawn into the syringe, in order to avoid possible contamination of the supply of the second ingredient. Even then it may be difficult to complete this procedure without rendering the outlet portion of the syringe non-sterile, particularly by extended contact with ambient air.
Another technique that can be employed utilizes a syringe of generally conventional construction in which one ingredient has initially been loaded into the syringe, usually followed by a complete sterilization procedure for the external portion of the syringe. Again, however, it is often rather difficult to load the syringe with the second ingredient without affecting the sterile characteristics of the syringe. Moreover, in both of these procedures the manipulative steps on the part of the pharmacist or nurse or doctor are complex enough so that some difficulty may be experienced.
Specialized dual-compartment syringes have been proposed for the administration of two-ingredient medications. For one specialized syringe of this kind, reference may be made to Sarnoff et al. U.S. Pat. No. 3,326,215. A dual compartment syringe of this kind, however, is relatively costly and complex in construction, requiring structural members of different configuration from those used in conventional syringes. Moreover, filling a special purpose syringe of this kind can be quite difficult and creates other problems with regard to avoidance of contamination and maintenance of sterility.